I dont believe in God.
For that matter, I dont believe in any supernatural whatzit; Im an Occams Razor kind of guy. You want to believe that Supernatural Claim X is for real? Okay, fine. Have a ball! Go ahead and believe in whatever-it-is with my compliments. I may think youre silly to believe in X but what the heck, you X-believers probably think Im silly to not believe in X, right?
Mind you, my tolerance does have its limits. What if John Doe thinks its okay to abuse, threaten, assault, persecute, or outright murder people who dont share Does belief in Supernatural Claim X? Suppose Doe thinks that people who dont share his belief in X should be forced to behave as if they actually did believe in X? In either of those cases, I'd have to say that this Doe gink is a menace to society, and should be treated as such. What makes supernatural beliefs problematic, as I see it, is that such beliefs are completely unconstrained by Realityin practical terms, they really are all in your head. Which isnt necessarily a bad thing, in and of itself, I hasten to add! As Thomas Jefferson wrote regarding a specific class of supernatural beliefs, [I]t does me no injury for my neighbor to say there are twenty gods, or no God. It neither picks my pocket nor breaks my leg. Of course, Jefferson was implicitly assuming that his neighbor shares his (Jeffersons) lack of concern about other peoples beliefs. When this isnt truewhen someone is very concerned indeed about what their neighbors do or dont believewell, in that case, things can get messy.
Whether youre talking about believers in X versus non-believers, or believers in X versus believers in Y, there are plenty of historical examples of exactly how messy things can get when people think their supernatural beliefs give them the right to interfere with the lives of those who do not share their beliefs. And thats when all the involved parties are the same species (namely, human)! How much messier can things get when you throw different species into the mix?
Alas, there is no easy answer to that question; there are too many relevant factors. Whats the precise nature of whichever supernatural beliefs are involved: Are non-believers shunned, respected, something else? Are believers supposed to make an effort to persuade others to believe as well, and if so, exactly how much of an effort is expected? What degrees of xenophilia/xenophobia are exhibited by each of the involved species? How easily can the involved species communicate with one another? How does each of the involved cultures feel about supernatural beliefsare such beliefs respected, reviled, ignored, something else? And so on.
On the plus side, this multiplicity of relevant factors means that any author whos interested in exploring this kind of cultural clash has justification for pretty much any scenario they feel like writing about. It's merely a matter of selecting the right set of initial conditions!